Building a bench supply without altering the ATX psu

[FozzTexx] has been using a bench supply he made from an AT PSU for years. He put a lot of work into that one, removing unnecessary wires, mounting banana plug jacks on the metal case, and adding an on/off switch and labels. But if it ever dies on him it will be a major pain to do all that work again in order to replace it. When he set out to build another bench supply from an ATX PSU he decided to do so without altering the PSU. This way he can easily swap it out for a different one if he ever needs to.

The hardest part of the hack was sourcing connectors. But with the parts in hand he’s able to just plug the faceplate into the stock connector. This gives him access to all of the voltages, and provides an on/off switch and indicator light. He might also want to add the option of resetting the unit if the over-current protection kicks in.

I’ve been powering the heat and lights for my vivarium off ATX power supplies for close on 6 years now. Salvaged the connector off a dead motherboard like you say. I’m actually only on my second PSU and it’s on 24/7. The first one only died because the fan seized and it overheated.

I’ve been saying this too, for years. PC power supplies seem so fragile, you fry one, then what of all your efforts to mod it for benchtop use. Just throw it away and plug in a new one, forget the mods. I agree 100% with FozzTexx.

Thanks for the link Hackaday! I can’t believe how much traffic you guys send! I was *not* prepared. :-)

I see people posting links to connectors, but the connectors so far are PCB mount ones. The ones I used in my build hang from the end of a cable and are crimped and don’t require any soldering or heat shrink tubing for insulating bare wires. They aren’t perfect, the clip is in slightly the wrong place, but they otherwise fit perfectly.

Yes that was my backup plan, however I was on a mission to hunt down those connectors. I really wanted to figure out what they were and place to get them from. I prefer being able to make my own cables. The pins and connectors themselves are really cheap and I already have the tools for crimping the pins on.

i gave up because banana jacks and plugs are the most expensive part i’ve ever seen in my life.

Really? How much are you seeing them for? I got 100 banana males for $13 shipped. The binding posts cost a little more, I got 10 for $4 shipped (those were screw-type binding posts with banana jacks, low-profile banana-only jacks are even cheaper).

Not sure what kind of prices you’re seeing, or what you consider expensive.

The cheapest source I know offhand is allelectronics.com. Panel mount banana jacks $0.60, plugs $0.50. A discount if you buy 10 or more.

Electronics Goldmine also have some for just a little more. Newark has tons, but be careful about the “direct ship” items as they will drastically increase shipping cost.

You can make do with all one color, if you color code them with colored electrical tape or paint. A colored heat shrink assortment will let you color code wires and cables by attaching a small length at either end, which is where you’re going to look to identify it anyway; and saves you from having to buy wires in umpteen different colors.

If you are going to use a ATX power supply for other purposes you really, and I can’t emphasize this enough, really need some form of protection between the power supply and the device being powered. Fuses should be a bare minimum, a crowbar circuit would be better. The problem is that pc supplies usually are high amperage, if you feed something like an arduino with the 5V output and you happen to wire anything wrong, you are going to destroy your circuit long before the ATX supply shuts off.

I have built some bench supplies from AT/ATX power supplies, for my own usage and for my school’s robotics club.
Actually, the first thing I do before even taking off the screws is to short-cut the different supplies : +5V to ground, +12V to ground, +5V to +12V, etc.
If the PSU gives up the ghost, then it surely wasn’t up to the task, as a lab PSU must be able to withstand some abuse and misuse :x
If the PSU survives, then it’s worth taking it apart and start modding !

The ATX supplys are switched and regulated. For me this does not consider to be a ‘bench supply’. I’ve seem someone build a cccv (constant current, constant voltage) out of a ATX power supply. This is allot more interesting to me. When do you need just 5V or 12V? Also couldn’t you just use a breakout from Sparkfun?

I’ve yet to find a easy solution for altering these supply’s to cccv. (If the supply is a brand new one it will be repeatable in future!)

I guess I’m pretty lucky where I live, we have a mom & pop electronics store that has all sorts of whacky molex connectors, including a full set for computer PSUs, and a few for wierd car stereos.

I always found it odd the strange assortment of things they’d stock like 2 & 4 pin connectors with the tab (like an old 3 1/2 floppy disk power connector) but not the 3 pin version (like for a motherboard fan). They had 1mm headers, but wouldn’t carry the sockets for them.

Good idea! I’ve always thought it was inconvenient to modify the actual PSU in case it breaks. I build a little adapter box that breaks out the ATX connector to binding posts. It’s pretty compact and seems to work quite well.